Field of the Invention
The present invention relates to wireless communication and, most particularly, to a method and apparatus for transmitting a frame in a wireless LAN.
Related Art
The range of channel bandwidths that are available for usage in the legacy wireless LAN system has become diverse from 20 MHz to 160 MHz. Accordingly, deciding an adequate channel bandwidth for the communication between a transmitting user equipment and a receiving user equipment has become a crucial factor in determining Wi-Fi performance.
In order to decide an adequate channel bandwidth for the communication between the transmitting user equipment and the receiving user equipment, a dynamic channel bandwidth configuration protocol, which is based on a RTS(request to send) frame and a CTS(clear to send) frame, has been developed starting from IEEE 802.11ac. The initial RTS frame and CTS frame have been devised to resolve the hidden node issue and to reduce data frame collision overhead. Before transmitting a data frame, the transmitting user equipment transmits a RTS frame to the receiving user equipment. After receiving the RTS frame, the target user equipment sends a response to the transmitting user equipment by using the CTS frame. Third party user equipments that have received the RTS frame and the CTS control frame may delay medium access for a predetermined period of time for the protection of data frame that are to be transmitted later on.
Referring to the dynamic channel bandwidth configuration protocol, which has been supported starting from IEEE 802.11ac, the transmitting user equipment may transmit a RTS frame through a wide band exceeding a channel bandwidth of 20 MHz, and the target user equipment may send a response with a CTS frame in accordance with a channel bandwidth that can be currently used by the corresponding target user equipment. For example, in case the transmitting user equipment wishes to use a channel bandwidth of 160 MHz, the RTS frame is transmitted through a 160 MHz channel bandwidth. In case the channel bandwidth that is currently available for usage of the target user equipment corresponds to 80 MHz, the target user equipment transmits the CTS frame through a 80 MHz channel bandwidth. In case the transmitting user equipment that has transmitted the RTS frame receives a CTS frame through a channel bandwidth of 80 MHz, the data frame that is transmitted afterwards to the target user equipment by the transmitting user equipment should be equal to or smaller than the 80 MHz channel bandwidth.